Chess variant where the black and white armies swapped initial position. However, movement of pawns did not change, so all pawns are only one step away from promoting, and nothing but their own pieces block this happening.
Otherwise the rules of chess apply.
Initially pieces block each other. The knight is the only piece that can move. Thereafter the pawns standing in front of the knights can move (and promote), and so free up all the pieces.
Usually the game is soon full of queens. Minor pieces become less valuable.
Example for opening:
G. P. Jelliss wrote about it in 1991[ChVar.com]